Get OAuth2TokenService working on Android.

sync/android/java/src/org/chromium/sync/signin/AccountManagerHelper.java

Index: sync/android/java/src/org/chromium/sync/signin/AccountManagerHelper.java
diff --git a/sync/android/java/src/org/chromium/sync/signin/AccountManagerHelper.java b/sync/android/java/src/org/chromium/sync/signin/AccountManagerHelper.java
index 882f90d4bf82290dd8f4061b669c3464c28e38c4..7952f4e3bcf091da88f3daac7e83f520a337deda 100644
--- a/sync/android/java/src/org/chromium/sync/signin/AccountManagerHelper.java
+++ b/sync/android/java/src/org/chromium/sync/signin/AccountManagerHelper.java
@@ -306,4 +306,11 @@ public class AccountManagerHelper {
         getAuthTokenAsynchronously(
             null, account, authTokenType, callback, numTries, errorEncountered, null);
     }
+
+    /**
+     * Removes an auth token from the AccountManager's cache.
+     */
+    public void invalidateAuthToken(String accountType, String authToken) {
+        mAccountManager.invalidateAuthToken(accountType, authToken);
+    }
 }